Heavy-contour 18" barrel is machined from high-grade stainless steel alloy, with a non-reflective matte black Teflon exterior finish. Chambered for 5.56mm NATO ammunition, 6-groove button rifled with a 1-8" twist. Extra length gives additional velocity for better potential long-range accuracy, with M4 feed ramps in the barrel extension and a rifle-length gas system for an extra measure of reliability. Compatible with any standard AR-15 upper.
AR-15, Issue:09, Page:102
Big Book Catalog, Issue:66, Page:016
SPECS: 416 stainless steel, natural silver finish. 18” OAL. .750” O.D. at gas block, .875” O.D. under handguard. Chambered for 5.56 x 45mm NATO ammunition (also accepts .223 Remington). Button-rifled, 6 grooves, 1-8” twist. ½” x 28 tpi muzzle threads. Rifle-length gas system.